feat: run Corefile check before run

[lidel]

Quality of life improvement, makes sure config is correctly loaded and the necessary plugins are present

Before

$ docker run --rm -it --net=host ghcr.io/ipshipyard/p2p-forge:v0.6.1
p2p-forge v0.6.1 2025-07-30-bdc3d05-dirty
CoreDNS-1.11.3
linux/amd64, go1.23.11,
p2p-forge v0.6.1 2025-07-30-bdc3d05-dirty
no action found for directive 'whoami' with server type 'dns' (missing a plugin?)

This PR

$ docker run --rm -it --net=host p2p-forge-dev
p2p-forge v0.6.1 2025-07-30-bdc3d05-dirty

Error: Configuration issue detected.

p2p-forge requires a Corefile with 'acme' and 'ipparser' plugins.
This error occurs when running without a proper Corefile or with
a generic CoreDNS config missing p2p-forge-specific plugins.

For detailed usage instructions, see: https://github.com/ipshipyard/p2p-forge#usage

Local development:
  ./p2p-forge -conf Corefile.local-dev -dns.port 5354

Production deployment:
  ./p2p-forge -conf Corefile
  (Note: Use production-appropriate Corefile, not Corefile.local-dev)

Docker:
  docker run --rm -it --net=host -v ./Corefile.local-dev:/p2p-forge/Corefile.local-dev ghcr.io/ipshipyard/p2p-forge -conf /p2p-forge/Corefile.local-dev -dns.port 5354

[codecov]

Codecov Report

❌ Patch coverage is 70.58824% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.50%. Comparing base (bdc3d05) to head (00de0ca).

Files with missing lines	Patch %	Lines
main.go	70.58%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #77      +/-   ##
==========================================
+ Coverage   62.04%   62.50%   +0.45%     
==========================================
  Files          11       11              
  Lines        1220     1288      +68     
==========================================
+ Hits          757      805      +48     
- Misses        391      411      +20     
  Partials       72       72              

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